1. Field of the Invention
The present invention relates to an objective lens unit for use in an optical pickup, and more particularly to an objective lens unit that makes it possible to reliably fix an objective lens with a small amount of an adhesive.
2. Description of the Related Art
As an example of an objective lens, one shown in FIGS. 5 and 6 is conventionally known. This objective lens unit is arranged such that a light passage hole 4 is penetratingly provided in a distal end portion of a holder 3 which is slidable in focusing directions a and b along a shaft 2 on an actuating base 1 and is swingable about the shaft 2 in tracking directions c and d. Further, a fitting groove 5 whose diameter is greater than that of the light passage hole 4 is concentrically formed at one end portion of the light passage hole 4, thereby forming a lens receiving seat 6 on an inner peripheral surface of the light passage hole 4. An objective lens OL fitted in the light passage hole 4 is mounted on the lens receiving seat 6 and is fixed in the holder 3. It should be noted that reference numeral 7 denotes a focusing coil, 8 denotes a tracking coil, and 9 denotes a magnet.
In the above-described configuration, as the focusing coil 7 is energized and is hence excited, the holder 3 is slid in the focusing direction a or b along the shaft 2 to adjust the focus of the objective lens OL. As the tracking coil 8 is energized and is hence excited, the holder 3 is swung about the shaft 2 in the tracking direction c or d, thereby causing the objective lens OL to follow a predetermined track of a disk.
As one example of a technique for fixing the objective lens OL to the holder 3, one disclosed in patent document 1 is known. In this technique, as shown in FIGS. 7 and 8, two rectangular filling recesses 11, in each of which a bottom surface 11a is set in a substantially horizontal state and inner side surfaces are set in a substantially vertical state, are formed on an inner peripheral surface of the fitting groove 5 at an opposing angle of 180 degrees. The objective lens OL fitted in the light passage hole 4 is mounted on the lens receiving seat 6, and an ultraviolet curing adhesive UV is filled into each filling recess 11 through a nozzle 12 of an adhesive applicator, as shown in FIGS. 9A and 9B. By allowing the adhesive UV to cure on application of ultraviolet rays thereto, the objective lens OL is fixed to the holder 3.
The above described structure is disclosed in JP-A-11-110800.